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64 | III. Biotope and animal associations this cannot be said for animals, but the biotope becomes suitable for animal life as soon as plants colonise the area. The plant cover, for animals, represents space, an energy source and conditions for growth, whereas a biotope for animals is nothing other than the space that provides conditions for plants plus the plant cover. The concept of the biotope is, therefore, not the same for plants and animals. The plant world needs fewer preconditions from the biotope than the animals because, for the latter, the plant cover is an essential component. A certain requirement for a biotope can be like this; for example, the herbal understory layer of a forest needs a more or less closed canopy as an essential condition. From a zoocoenological point of view, such biotopes can be characterised by plant associations that include (after Sod, 1945): emersiherbosa (swamp vegetation), altoherbosa (tall shrub vegetation), sempervirentiherbosa (evergreen meadows), duriherbosa (dry grasslands), mobilideserta (sandy vegetation), rupideserta (rock vegetation), arvideserta (vegetation of cultivated areas), aciculilignosa (needle-leaved shrubbery or forests), aestifruticeta (deciduous shrubbery), and aestilignosa (deciduous forests). Theoretically, this view agrees with Tischler’s (1948) position, who also sees the biotope as various associative units of plant cover. He goes one step further, though, and uses the ordo (-etalia) level of Tuxen’s plant sociological taxonomy. It is very likely that, at least in some cases, we have to go to this depth of classification, and the categories detailed above can be interpreted so that the formation group is the uppermost, and the ordo is the lowermost, limit for identifying the biotope. The biotope of animal associations is also envisaged in the framework of plant associations by Nagy (1944, 1947), but he goes further by calling certain associations “biotope type’, while identifying certain features (soil structure, slope, direction of slope, degree of vegetative cover, altitude) that relate to the structure of the biotope, and which can be decisive factors for shaping the ecoclimate. Schwenke (1953) disagrees with Tischler, but only in the sense that he does not think that biotopes are suitable to delimit a zoocoenosis, which can only be made based on species composition; otherwise, he also sees the biotope as the dominant plant association (Schwenke, 1953). Rabeler (1937, 1952) goes the furthest in this regard, and considers all associations as biotopes; accordingly, the 170 plant associations described from northern Germany allow him to distinguish an equal number of biotopes. We have to mention that there are known biotopes that have drifted far from the theoretically essential plant cover. The zoocoenoses of deep sea do not have producent elements (Thienemann, 1939), and rely on resources drifting down from above. Caves also represent a very special biotope (Dudich, 1932) where, apart from chemosynthetic producents, the zoocoenosis also depends on organic material from outside.
